Effect of parathyroid hormone on jejunal electrolyte and water transport and cyclic nucleotide formation in the rat.

The effect of parathyroid hormone (PTH) on jejunal sodium, calcium, and water transport in situ was studied in thyroparathyroidectomized rats using the ligated loop instillation model. The acute administration of bovine PTH to the animals induced a significant increase in net sodium and water secretion when compared to animals receiving the vehicle only. This effect was due to an increase in unidirectional mucosa-to-lumen sodium flux. However, no change of calcium fluxes was observed. This acute in vivo effect on PTH could not be explained by an action via the adenyl or guanyl cyclase systems since bPTH failed to induce changes of cAMP or cGMP formation in isolated jejunal cells. Thus, other so far not elucidated mechanisms of action must be involved.